The present invention relates to a data transfer apparatus which is effective for a case of transferring comparatively large capacity data by a comparatively unreliable interface, for example, a case of reading data out of a memory, writing data into the memory, or transferring address of the memory.
While ranges of use of information processing apparatus, such as a computer, and the like have been enlarged, processing speed of these apparatus have been improved. Under the circumstances, chances in which large capacity data are processed by those apparatus have also been increased. Especially in a system having a large constitution, when the large capacity data are transferred between apparatus, errors are apt to be caused to occur at the same time over a plurality of bits. Accordingly, desired is a reliable data transfer apparatus capable of relieving such errors simultaneously generated over a plurality of bits.
Even in a conventional data transfer apparatus, some countermeasures are taken, in a case that the errors are simultaneously generated over a plurality of bits and thereby correction of the errors becomes impossible. Namely, a countermeasure is taken so that a system carrying out the data transfer may be immediately stopped and then reasons of the errors may be checked. Further, another countermeasure is taken so that the corresponding data may be re-issued from a data output section or data stored in a shunting buffer, such as a re-sending buffer, or the like may be re-issued.
Moreover, yet another countermeasure is taken as follows, in a technique disclosed in an official gazette of unexamined Japanese patent publication, No.2000-244530. Namely, data to be transmitted are divided into a plurality of data each having a predetermined quantity of data and then the divided data are stored in a plurality of sending buffers, respectively. Further, each storing address of these data is memorized by an address memorizing means. Accordingly, in a case that data are transmitted to a transmission destination by a transmission means and then errors are detected, a sending buffer corresponding to the erroneous data is deduced from the address memorizing means and thereby transmission data are re-sent from the deduced sending buffer.
However, in the countermeasure that the system is checked as soon as the correction of the errors becomes impossible, the system is unconditionally stopped for a predetermined time to carry out the check of the system. As a result, a problem of deterioration of reliability is inevitably caused to occur by interruption of the data in a system that data transfer needs to be continuously carried out.
Further, in the countermeasure that the corresponding data are re-issued from the data output section, during the re-issue, progress of transmission of the data to be re-issued is, of course, delayed by the time for the re-issue itself. However, the countermeasure has a problem that progress of transmission of data other than the re-issue data is delayed similarly to that. For example, it is assumed that two kinds of data, namely, data to be sent to a predetermined memory and data to be sent to a predetermined input device, and that a trouble is caused to occur in the data sent to the predetermined memory. In this case, the data to be sent to the predetermined memory are interrupted into data to be outputted in the data output section. As a result, under the influence thereof, progress of transmission of the data to be sent to the predetermined input device is also delayed by the time for the interruption. Similar problem is also caused to occur in the technique disclosed in the official gazette of unexamined Japanese patent publication, No.2000-244530. Accordingly, in these techniques, as regards data having no relation with the troubled data and desired to be transmitted without delay, a problem of deterioration of reliability of the data transfer is inevitably caused to occur.
In order to avoid such a problem, as mentioned before, a proposal is made about the countermeasure that the data are re-sent from the shunting buffer by way of a transmission route different from the data output section. However, in this proposal, it is necessary to prepare not only a special buffer, that is, the shunting buffer but also a special transmission route. As a result, the proposal has a problem that cost of the system is increased by increase of quantity of hardware. In addition, in a case that the corresponding data are re-issued from the shunting buffer at the time of generation of trouble, it is difficult to recognize boundary of the data, order of transferring the data, and the like. Therefore, the re-sent data cannot be recognized correctly in the transmission destination. This sometimes brings about such a phenomenon that, what is called, transformation of characters is caused to occur.